Method for producing liquid fertilizer and system for producing liquid fertilizer

Abstract

The object of the present invention is to provide a method for producing liquid fertilizer using digestate as a raw material, which can efficiently separate both nitrogen and water while adjusting the nitrogen content of the resulting concentrated liquid to a desired value, and a system that can be used to carry out this method. [Solution] The above objective can be achieved by a method for producing liquid fertilizer, which includes an ammonia separation step, a water separation step, and a mixing step, wherein the ammonia separation step is a step of separating ammonia from the digestate to obtain a processed liquid, the water separation step is a step of separating water from the processed liquid to obtain a concentrated liquid, and the mixing step is a step of mixing the ammonia and the concentrated liquid to obtain liquid fertilizer.

Description

[Technical Field]

[0001] The present invention relates to a method for producing liquid fertilizer from digestate obtained after methane fermentation, and a system used for producing liquid fertilizer from digestate. [Background technology]

[0002] Organic resources derived from plants and animals are known as biomass and are attracting attention as a renewable energy source that can replace fossil fuels. For example, it is known that biogas can be produced by biochemically converting waste biomass such as livestock manure (cattle, pigs, chickens, etc.), food waste, food processing plant residues, expired food, agricultural crop residues (rice straw, wheat straw, etc.), sewage sludge, human waste, energy crops (corn, sorghum, etc.), and waste cooking oil.

[0003] Biogas production utilizes methane fermentation technology. Specifically, waste resources are subjected to methane fermentation, which uses anaerobic microorganisms to digest organic matter, thereby producing methane gas (CH4) as biogas.

[0004] In methane fermentation, if the raw materials are dry, such as food waste and some livestock manure (e.g., laying hen manure), or if the nitrogen concentration is too high (causing ammonia inhibition), a large amount of water is added to dilute and adjust the raw materials to promote fermentation. As a result, a large amount of digestate, which is the fermentation residue, is produced along with biogas. The digestate is separated into solid and liquid components by solid-liquid separation treatment, and the solid component is used as solid fertilizer.

[0005] Digestive fluid is more than 90% water and lacks sufficient nitrogen (N), potassium (K), and phosphorus (P), which are the most important nutrients. Therefore, using it as is as liquid fertilizer is inefficient in terms of agricultural work and liquid fertilizer distribution. As a method for producing liquid fertilizer by concentrating digestive fluid, for example, a method is known in which the pH value of the liquid portion of the digestive fluid is adjusted to 5.0 or less with sulfuric acid, and then the resulting acidic adjusted solution is evaporated and concentrated to produce liquid fertilizer (for example, Patent Document 1).

[0006] Furthermore, it is known that by directly treating the digested liquid with ultrasound without subjecting it to solid-liquid separation, ammonia gas can be separated along with water, and the ammonia gas can be removed and recovered as a (NH4)2SO4 solution by contacting it with a sulfuric acid solution (for example, Non-Patent Document 1). [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 7064104 [Non-patent literature]

[0008] [Non-Patent Document 1] Junichi Mori et al., Abstract C10-2-O, "Influencing Factors and Application Effects of Ammonia Recovery from Methane Fermentation Wastewater Using Ultrasonic Atomization," 36th Annual Meeting of the Japan Society of Waste Management and Resource Recycling. [Overview of the project] [Problems that the invention aims to solve]

[0009] However, the methods described in Patent Document 1 and Non-Patent Document 1 are both one-step methods for recovering nitrogen and water from digestate, making it difficult to efficiently separate both nitrogen and water. Furthermore, these methods make it difficult to control the ammonia removal efficiency, and thus difficult to adjust the nitrogen content of the resulting recovered liquid.

[0010] On the other hand, there are virtually no known methods for producing liquid fertilizer that use digestate as a raw material, efficiently separate both nitrogen and water, and adjust the nitrogen content of the resulting concentrated liquid to a desired value.

[0011] Therefore, the object of the present invention is to provide a method for producing liquid fertilizer that uses digestate as a raw material, efficiently separates both nitrogen and water, and adjusts the nitrogen content of the resulting concentrated liquid to a desired value, and a system that can be used to carry out this method. [Means for solving the problem]

[0012] As a result of diligent research aimed at solving the above problems, the present inventors have found that by separating ammonia and water from the liquid obtained by subjecting the residue after methane fermentation to solid-liquid separation (referred to as digestate in this specification) in a stepwise manner, both nitrogen and water in the digestate can be efficiently separated, and that by appropriately mixing the separated ammonia with the concentrated liquid, a liquid fertilizer having the desired nitrogen content can be obtained.

[0013] Based on these findings, the inventors, through repeated trial and error, succeeded in creating a method for producing liquid fertilizer and a system that can be used to implement this method, thereby solving the problems of the present invention. This invention is completed based on the first-of-its-kind findings and successful examples achieved by the inventors.

[0014] In other words, according to each aspect of the present invention, the following embodiments are provided. [1] A method for producing liquid fertilizer, It includes an ammonia separation step, a water separation step, and a mixing step. The ammonia separation step is a step of separating ammonia from the digestate to obtain a processed liquid. The water separation step is a step of separating water from the processing liquid to obtain a concentrated liquid, and The mixing step is a step of mixing the ammonia and the concentrated liquid to obtain liquid fertilizer. The above method. [2] The ammonia separation step is a step of separating ammonia from the digestion liquid by at least one treatment selected from the group consisting of aeration treatment, atomization treatment, and vaporization treatment to obtain a treatment liquid, according to the method described in item [1]. [3] The water separation step is a step of separating water from the treatment liquid by at least one treatment selected from the group consisting of atomization treatment and vaporization treatment to obtain a concentrated liquid, according to the method described in item [1]. [4] Further includes a water recovery step, The water recovery step is a step of recovering the water separated in the water separation step. The method described in item [1]. [5] A system for manufacturing liquid fertilizer, Comprising ammonia separation means, water separation means, and mixing means, The ammonia separation means is configured to separate ammonia from the digestion liquid to obtain a treatment liquid, The water separation means is configured to separate water from the treatment liquid to obtain a concentrated liquid, and The mixing means is configured to mix the ammonia and the concentrated liquid to obtain liquid fertilizer. The above system. [6] The ammonia separation means is at least one tank selected from the group consisting of an aeration tank, an atomization treatment tank, and a vaporization treatment tank, according to the system described in item [5]. [7] The water separation means is at least one tank selected from the group consisting of an atomization treatment tank and a vaporization treatment tank, according to the system described in item [5]. [8] Further includes water recovery means, The water recovery means is configured to recover the water separated by the water separation means. The system described in item [5]. [9] The digestion liquid is the digestion liquid subjected to solid-liquid separation, according to the method described in item [1] or the system described in item [5]. [Effect of the Invention]

[0015] According to the present invention, both nitrogen and water can be efficiently separated from the digestate. According to the present invention, the nitrogen content of liquid fertilizer can be adjusted to a desired value by adjusting the ammonia concentration, and as a result, liquid fertilizer having the desired nutrients can be produced. In other words, according to the present invention, liquid fertilizer can be produced by efficiently concentrating and adjusting the nutrients of the digestate. According to the present invention, the digestate can be concentrated effectively and economically without damaging the nitrogen components useful as fertilizer, and a liquid fertilizer that is both fast-acting and long-lasting can be produced.

[0016] Furthermore, according to the present invention, it is possible to avoid the use of chemicals such as flocculants and to obtain a concentrated digestate without impairing the nutritional components, making it possible to distribute the obtained concentrated liquid as liquid fertilizer. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is a flowchart illustrating a method for producing liquid fertilizer according to one embodiment of the present invention. [Figure 2] Figure 2 is a flowchart illustrating a method for producing liquid fertilizer according to another embodiment of the present invention. [Figure 3] Figure 3 is a schematic diagram of the liquid fertilizer production system 1. [Figure 4] Figure 4 is a schematic diagram of the liquid fertilizer production system 2. [Modes for carrying out the invention]

[0018] The details of each aspect of the present invention will be described below, but the present invention can take various forms insofar as it achieves its objective.

[0019] In this specification, unless otherwise specified, each term is used in the sense commonly used by those skilled in the art in the fields of methane fermentation, liquid fertilizers, wastewater treatment, etc., and should not be interpreted as having an unduly restrictive meaning. Furthermore, since the assumptions and theories made herein are based on the inventors' prior knowledge and experience, the present invention is not limited solely to such assumptions and theories.

[0020] "Comprise," "contain," and "include" mean that elements other than those explicitly included can be added (synonymous with "at least include"), but they also encompass "consist of" and "essentially consist of." In other words, "comprise" can mean including the explicitly included elements and any one or more of those elements, consisting of the explicitly included elements, or essentially consisting of the explicitly included elements. "Have" is synonymous with "comprise." Elements include limitations such as parts, means, components, processes, conditions, and parameters. "and / or" and its abbreviated form " / " mean any one, any combination of two or more, or all combinations of the listed related items. Throughout this specification, unless the context clearly indicates a singular term, the terms are to be plural.

[0021] [Summary of the Invention] One aspect of the present invention is a method for producing liquid fertilizer. A method according to one embodiment of the present invention includes an ammonia separation step, a water separation step, and a mixing step. The ammonia separation step is a step of separating ammonia from the digestate to obtain a processed liquid. The water separation step is a step of separating water from the processed liquid to obtain a concentrated liquid. The mixing step is a step of mixing ammonia and the concentrated liquid to obtain liquid fertilizer.

[0022] Another aspect of the present invention is a system for producing liquid fertilizer. A system according to one embodiment of the present invention comprises an ammonia separation means, a water separation means, and a mixing means. The ammonia separation means is configured to separate ammonia from the digestate to obtain a processed liquid. The water separation means is configured to separate water from the processed liquid to obtain a concentrated liquid. The mixing means is configured to mix the ammonia and the concentrated liquid to obtain liquid fertilizer.

[0023] [Method for manufacturing liquid fertilizer] A method according to one aspect of the present invention involves separating a digestate into ammonia and a treatment liquid, then separating the resulting treatment liquid into water and a concentrated liquid, and then mixing the resulting ammonia and concentrated liquid to obtain a liquid fertilizer.

[0024] A method according to one aspect of the present invention includes an ammonia separation step, which is a step of separating ammonia from the digestate to obtain a processed liquid.

[0025] The digestate can be any liquid obtained by subjecting the residue after methane fermentation to solid-liquid separation. For example, it can be the liquid obtained by subjecting the residue generated in methane gas production, which is produced by biochemically converting waste biomass with methane-producing bacteria, to solid-liquid separation. The digestate contains ammonium ions (NH4 + A product with a concentration of 1,000 mg / L or higher, from which insoluble solids have been removed, is preferred, but is not limited thereto.

[0026] The ammonia separation step involves separating ammonia from the digestate, preferably by volatilizing the ammonia in the digestate to obtain a liquid (processed liquid) that does not contain ammonia or has a reduced amount of ammonia. The separation of ammonia can be carried out by converting ammonium ions in the digestate into ammonia gas, for example, under conditions such that the following chemical formula holds true. NH4 + →NH3(gas)+H +

[0027] The digestate, which is the residue after methane fermentation, also contains dissolved carbon dioxide. Carbon dioxide is formed in the digestate, and then it dissociates to release hydrogen ions. CO2 + H2O ←→ H2CO3 ←→ H + +HCO3 - However, aeration releases carbon dioxide from the digestate, and as carbon dioxide decreases, carbon dioxide formation decreases, hydrogen ion concentration drops, and as a result the pH value rises. Ammonia gas begins to increase when the pH value is 8 or higher, and aeration releases the ammonia gas from the digestate, allowing for efficient separation of ammonia as a gas. Separation of ammonia is preferably carried out by aeration, for example, by passing air or an inert gas through the digestate. Aeration treatment of the digestate is performed to remove ammonium ions (NH4) from the digestate. + The aeration should be carried out under conditions that convert the gas into ammonia gas (NH3). The aeration method can be carried out by placing a ventilation means such as a diffuser plate or sparger on a part of the bottom or side of the tank containing the digestate, and supplying a gas such as air to the ventilation means from a gas supply means such as a blower. The diffuser plate can be any porous material, for example, it may be disc-shaped or flat; the pore diameter may be 1.0 mm to 3.0 mm, preferably 1.5 mm to 2.0 mm; and the pore pitch may be 5 mm to 30 mm, preferably 10 mm to 20 mm, but it can be appropriately selected depending on the amount of digestate to be processed and the size of the digestate storage tank. The aeration treatment time should be long enough for sufficient ammonia gas to be generated, for example, several minutes or more is preferred, and 1 hour to 3 days is more preferred.

[0028] The digestate may be used directly for ammonia separation, but it is preferable to pre-treat it to increase the efficiency of converting ammonium ions in the digestate to ammonia gas. Examples of pre-treatment of the digestate include, for example, if the pH of the digestate is neutral or acidic, pre-treatment using an alkaline agent to make the digestate preferably alkaline, more preferably with a pH of 8 to 10; and if the temperature of the digestate is relatively low, pre-treatment using a heater to raise the temperature of the digestate preferably to room temperature to high, more preferably 25°C to 45°C, and even more preferably 35°C to 40°C. The equilibrium of ammonia is shown, for example, by the Henderson-Hasselbalch equation, and according to Emerson et al. (1975), J. Fish. Res. Board Can., 32, 2379-2383, the approximate formula pKa = 0.09018 + T2729.92 holds for temperature T (K). According to this, when the temperature of the digestate is between 25°C and 30°C, setting the pH value to 8.5 or higher tends to increase the amount of ammonia gas produced, and when the temperature of the digestate is 40°C or higher, setting the pH value to 8.0 or higher tends to increase the amount of ammonia gas produced.

[0029] For aeration of the digestate, it is preferable to use the gas generated during the subsequent mixing process as the gas supply source. That is, it is preferable to use a blower to draw in the exhaust gas generated when ammonia and the concentrate are mixed, and then discharge the drawn-in gas into the digestate.

[0030] The ammonia separation step yields a treated liquid from which ammonia has been removed or whose ammonia concentration has been reduced. In the treated liquid obtained after aeration, the nitrogen source exists as nitrate nitrogen and / or nitrite nitrogen. Since nitrate nitrogen / nitrite nitrogen does not vaporize, it may be present in the concentrated liquid of the next step.

[0031] A method according to one aspect of the present invention includes a water separation step, which is a step of separating water from the processed liquid obtained in the ammonia separation step to obtain a concentrated liquid.

[0032] The separation of water from the treatment liquid can be carried out in such a way that the volume of the treatment liquid decreases. For example, it is preferable to carry out the separation in such a way that the water in the treatment liquid evaporates. It is more preferable to use a vaporization treatment to dry the water in the treatment liquid, an atomization treatment to turn the water in the treatment liquid into water vapor, and to carry out these simultaneously or in parallel.

[0033] Various drying methods can be employed for the vaporization process, including natural (sun) drying using heat such as sunlight, air, and wind from a blower, heat drying, reduced pressure drying, moisture absorption using pressure or temperature differences, and membrane separation drying. However, natural drying is preferred because it can be carried out with simple operations.

[0034] Atomization treatment can be any treatment that evaporates water, and examples include ultrasonic, jet, compressor, gas atomization, pressure, mesh, centrifugal, rotary, steam, heating, water atomization, and vaporization methods. However, the ultrasonic method is preferred because it can efficiently separate water and generate water vapor.

[0035] The vaporization and atomization treatments can be switched as appropriate according to the properties of the digestate, weather conditions, and installation environment conditions, and these can also be combined. For example, water may be separated by natural vaporization during the dry season and by atomization during the rainy season.

[0036] The water separation step yields a concentrated solution with a reduced volume compared to the treated solution. The volume of the concentrated solution only needs to be smaller than the volume of the treated solution; for example, it is preferably 1% to 70%, more preferably 1% to 60%, and even more preferably 1% to 50% of the volume of the treated solution. The water separation step can be carried out under conditions such as the time required to achieve the desired concentration ratio.

[0037] A method according to one aspect of the present invention includes a mixing step of mixing ammonia obtained in an ammonia separation step with a concentrated liquid obtained in a water separation step to obtain a liquid fertilizer.

[0038] The mixing step should be carried out so that the ammonia obtained in the ammonia separation step dissolves in the concentrated liquid obtained in the water separation step. For example, it is preferable to carry out the mixing step by blowing ammonia (gas) into the concentrated liquid.

[0039] The mixing of ammonia and the concentrate is preferably carried out under conditions that facilitate ammonia solubility in the concentrate. For example, the pH of the concentrate should be neutral to acidic, and the temperature of the concentrate should be below room temperature, for example, 20°C to 25°C. Furthermore, if the gas generated in the mixing process is used for aeration of the digestate, it is preferable to lower the pH of the concentrate than the pH of the digestate, and / or lower the temperature of the concentrate than the temperature of the digestate.

[0040] The mixing process yields a liquid fertilizer to which ammonia has been added. The ammonia concentration of the liquid fertilizer should be sufficiently higher than the ammonia concentration of the concentrate, and can be appropriately set to achieve the desired ammonia concentration. For example, the ammonia concentration of the liquid fertilizer, as total ammonia nitrogen, is preferably 1.1 to 30 times, more preferably 1.2 to 20 times, and even more preferably 1.3 to 10 times or 1.5 to 5 times, relative to the ammonia concentration of the concentrate. The mixing of ammonia and concentrate can be carried out under conditions such as time, which allows the ammonia concentration of the liquid fertilizer to reach the desired concentration.

[0041] Figure 1 is a flowchart of a method according to one embodiment of the present invention. As shown in Figure 1, in one embodiment of the present invention, the digestate is separated into a treatment liquid and ammonia by an ammonia separation step. Next, the treatment liquid is separated into a concentrated liquid and water by a water separation step. Then, the concentrated liquid is mixed with the ammonia separated in the ammonia separation step by a mixing step to obtain liquid fertilizer.

[0042] In one embodiment of the present invention, each step may be carried out in a batch process, or each step may be carried out in a continuous process. In the batch process, the ammonia separation step is carried out, followed by the water separation step, and then the mixing step. For example, the ammonia separation step is carried out on the first day, the water separation step on the second day, and the mixing step on the third day. In the continuous process, the ammonia separation step, the water separation step, and the mixing step are carried out simultaneously and in parallel. The water separation step may be changed and controlled according to the season, such as sun drying in the dry season and moisture absorption drying in the rainy season, multiple methods may be used in combination to accelerate water separation, or the processing step may be branched into multiple lines and the treated water distributed in small amounts may be concentrated in parallel.

[0043] A method according to one aspect of the present invention preferably further includes a water recovery step for recovering the water separated in the water separation step. Figure 2 is a flow chart of another aspect of the present invention, which includes a water recovery step. As shown in Figure 2, a method according to one aspect of the present invention recovers the water separated in the water separation step. The recovered water can be used, for example, as dilution water for methane fermentation. That is, the recovered water can be added to and mixed with waste resources such as food residue, which are raw materials for methane fermentation, to obtain a raw material slurry. In methane gas production plants that use large amounts of water, the ability to recycle and reuse water, which is a valuable resource, is environmentally and economically advantageous. The amount of water that is depleted for liquid fertilizer may be supplemented with rainwater, surface water, etc.

[0044] In one embodiment of the present invention, when atomization is employed in the water separation step and 50% of the treated liquid is atomized (concentrated twice), the theoretical value of the concentration ratio is as follows. In other words, the digestive fluid has a pH of 8 and contains 1,500 mg of total ammonia nitrogen (TAN) (NH3 202 mg, NH4 + A digestate containing 1,298 mg of TAN is used. 1.0 L of the digestate is subjected to aeration treatment at 40°C. The properties of the treated solution are a pH of 9 and a TAN content of 183 mg (NH366 mg, NH4 +(117 mg). The treatment liquid is concentrated twice by ultrasonic treatment. When the obtained concentrated liquid is brought to 25°C and the exhaust gas from the aeration treatment is passed through, the pH value is 8, and the TAN is 1,315 mg (NH3 70 mg, NH4 + A liquid fertilizer of 0.5 L with a TAN of 1,245 mg is obtained. Since the TAN of the digested liquid is 1,500 mg / L and the TAN of the liquid fertilizer is 1,315 mg / 0.5 L (= 2,630 mg / L), a liquid fertilizer with the TAN concentrated 1.75 times is obtained.

[0045] [System for manufacturing liquid fertilizer] The system of one aspect of the present invention includes an ammonia separation means, a water separation means, and a mixing means. The system of one aspect of the present invention can be used, for example, to implement the method of one aspect of the present invention. The system of one aspect of the present invention is preferably configured to be able to implement each step included in the method of one aspect of the present invention.

[0046] Hereinafter, each aspect of the system of the present invention and its embodiments will be described with reference to the drawings. In each drawing, those having low relevance to the present invention are not shown. The arrows (→) in the drawings represent the flow directions of liquids and gases. P in the drawings indicates a pump. Note that the ammonia separation means, the water separation means, and the mixing means may have different shapes among the drawings, but the same numbers and symbols are used for convenience.

[0047] FIG. 3 is a schematic configuration diagram of a liquid fertilizer manufacturing system 1 including an ammonia separation means 10, a water separation means 20, and a mixing means 30, which is a system of one aspect of the present invention.

[0048] The ammonia separation means 10 has a tank structure with a diffuser plate 11 having a porous disk structure provided on the bottom side. The ammonia separation means 10 can store the digested liquid flowing in from the pipe L1 and can be aerated by a gas mainly composed of air flowing into the diffuser plate 11. The illustrated ammonia separation means 10 is an aeration tank.

[0049] The digestate stored in the ammonia separation means 10 is aerated to obtain a treated liquid W1. During this process, foam B1 is generated in the treated liquid W1 due to aeration. The ammonia separation means 10 may be equipped with a foreign matter recovery means, such as a demister, on the upper side of the tank to separate and remove solid matter, generated foam, and droplets from the digestate. The recovered foreign matter may be removed from the ammonia separation means 10 system as solid matter and sent to the methane fermentation process.

[0050] The ammonia separation means 10 may also include a temperature control means for adjusting the temperature of the tank, a chemical input means for adding chemicals such as pH adjusters, etc., in order to facilitate the generation of ammonia gas.

[0051] The gas flowing into the diffuser plate 11 contains or consists of exhaust gas from the mixing means 30, and this exhaust gas is sent to the diffuser plate 11 by blower BL1 through pipe L31. Aeration of the digestate releases ammonium ions (NH4) from the digestate. + The ) is converted into ammonia gas (NH3). The ammonia gas is sent through pipe L11 by blower BL2 into the liquid fertilizer W3 stored in mixing means 30. The treated liquid W1 obtained after aeration treatment in ammonia separation means 10 is sent through L12 to water separation means 20.

[0052] The water separation means 20 has a tank structure that can store the processing liquid W1 and has an open upper end. The water separation means 20 may be equipped with a drying means such as a blower, either in addition to or in conjunction with the open upper end. The illustrated water separation means 20 is a vaporization treatment tank. The water separation means 20 may also have a structure that recovers the evaporated water.

[0053] By separating water from the treatment liquid W1 stored in the water separation means 20, such as by evaporation, a concentrated liquid W2 with reduced volume is obtained. The concentrated liquid W2 is sent to the mixing means 30 through the pipe L21. The water separation means 20 may be equipped with a temperature control means, a chemical input means, etc., to facilitate the separation of water. When vaporization treatment is employed, the water separation means 20 preferably has a surface area 1 to 1,000 times, more preferably 2 to 200 times, that of the ammonia separation means in order to efficiently perform the vaporization treatment.

[0054] The mixing means 30 has a tank structure capable of storing the concentrated liquid W2. The end of the pipe L11 for supplying ammonia gas from the ammonia separation means 10 is positioned in the liquid stored in the mixing means 30. The mixing means 30 is equipped with a pipe L31 for supplying exhaust gas to the diffuser plate 11 of the ammonia separation means 10. The mixing means 30 mixes the concentrated liquid W2 from the water separation means 20 with ammonia gas from the ammonia separation means 10 to obtain liquid fertilizer W3. The injection of ammonia gas generates bubbles B2 in the liquid fertilizer W3.

[0055] The end of the pipe L11 placed inside the mixing means 30 may have a structure for dispersing gas as fine bubbles in the liquid, such as a diffuser plate or sparger. Furthermore, to facilitate the dissolution of ammonia gas, the mixing means 30 may be equipped with stirring means such as agitators, temperature control means, chemical injection means, etc. Also, the degassing of ammonia gas may be suppressed by pressurizing the inside of the mixing means 30.

[0056] The liquid fertilizer W3 produced by the mixing means 30 can be used as is, or as a liquid fertilizer that has been further processed or had its components adjusted, for plant cultivation in fields, gardens, and other areas.

[0057] Figure 4 is a schematic diagram of a liquid fertilizer production system 2, which is another embodiment of the present invention, and is equipped with three water separation means 20a, 20b, and 20c in addition to the ammonia separation means 10 and mixing means 30 of the liquid fertilizer production system 1. In the liquid fertilizer production system 2, the processed liquid produced by the ammonia separation means 10 is sent to the water separation means 20a, 20b, and 20c, respectively, through a pipe L12 that branches into three. The concentrated liquid produced by the water separation means 20a, 20b, and 20c is then sent to the mixing means 30 through a pipe L21 that branches into three.

[0058] As another embodiment of the present invention, there is a liquid fertilizer manufacturing system 3 that, in addition to the ammonia separation means 10 and mixing means 30 of the liquid fertilizer manufacturing system 1, includes a water separation means 20d equipped with an ultrasonic generating means 21 as an atomizing means, and a water recovery means 40 for recovering and storing the water vapor generated by the water separation means 20d. In this way, the water separation means 20d constitutes an atomizing treatment tank.

[0059] The ultrasonic generating means 21 provided by the water separation means 20d generates ultrasonic waves S1 in the processing liquid stored in the water separation means 20d, and the water in the processing liquid is sent as water vapor through the pipe L22 to the water recovery means 40.

[0060] The water recovery means 40 has a tank structure capable of storing the supplied steam as recovered water W4. The water recovery means 40 may also be equipped with a temperature control means, a chemical injection means, etc., to facilitate the condensation of steam. The recovered water W4 stored in the water recovery means 40 can be used, for example, as dilution water in the methane fermentation process. The water recovery means 40 may also be equipped with means to facilitate water recovery, such as bubbling, a demister, a cooling tower, a cyclone, or a microfiltration membrane.

[0061] [Another aspect of the present invention] Another aspect of the present invention is a methane fermentation method and a methane fermentation system. A methane fermentation method according to one aspect of the present invention includes a methane fermentation step of performing methane fermentation using recovered water and waste resources recovered in a liquid fertilizer production method according to one aspect of the present invention, and a solid-liquid separation step of subjecting the residue obtained from the methane fermentation step to solid-liquid separation to obtain a digestate. A methane fermentation system according to one aspect of the present invention includes a methane fermentation means configured to enable methane fermentation using recovered water and waste resources recovered in a liquid fertilizer production system according to one aspect of the present invention, and a solid-liquid separation means configured to obtain a digestate from the residue obtained from the methane fermentation means. The digestate obtained by a methane fermentation method and a methane fermentation means according to one aspect of the present invention can be used as a raw material for a liquid fertilizer production method and a liquid fertilizer production system according to one aspect of the present invention. [Industrial applicability]

[0062] A method and system according to one embodiment of the present invention can adjust the nitrogen content to a desired value by adjusting the ammonia concentration, and as a result can produce a liquid fertilizer having the desired nutrients, so that the resulting liquid fertilizer can be distributed and used as is. [Explanation of Symbols]

[0063] 1, 2, 3 Liquid fertilizer production system 10 Ammonia separation means 11 Aeration plate 20, 20a, 20b, 20c, 20d water separation means 21 Ultrasonic generating means 30 Mixing means 40 Water recovery methods P Pump

Claims

1. A method for producing liquid fertilizer, It includes an ammonia separation step, a water separation step, and a mixing step. The ammonia separation step is a step of separating ammonia from the digestate by aeration treatment to obtain a treated liquid. The water separation step is a step of separating water from the processing liquid to obtain a concentrated liquid, and The mixing step is a step of mixing the ammonia and the concentrated liquid to obtain liquid fertilizer. The aforementioned method.

2. The method according to claim 1, wherein the water separation step is a step of separating water from the processing liquid by at least one treatment selected from the group consisting of atomization and vaporization to obtain a concentrated liquid.

3. Furthermore, including a water recovery process, The water recovery step is a step of recovering the water separated in the water separation step. The method according to claim 1.

4. A system for manufacturing liquid fertilizer, It comprises an ammonia separation means, a water separation means, and a mixing means, The ammonia separation means is an aeration treatment tank configured to separate ammonia from the digestate to obtain a treated liquid, The water separation means is configured to separate water from the processing liquid to obtain a concentrated liquid, and The mixing means is configured to mix the ammonia and the concentrated liquid to obtain a liquid fertilizer. The aforementioned system.

5. The system according to claim 4, wherein the water separation means is at least one tank selected from the group consisting of an atomizing tank and a vaporizing tank.

6. Furthermore, it is equipped with a water recovery mechanism, The water recovery means is configured to recover the water separated by the water separation means. The system according to claim 4.

7. The method according to claim 1, wherein the digestate is a digestate subjected to solid-liquid separation.

8. The system according to claim 4, wherein the digestate is a digestate subjected to solid-liquid separation.

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